Responsibility for the death of a Chinese woman on an escalator over the weekend lay with the manufacturer and the shopping mall where it was operating, an official investigation has found.

Xiang Liujuan, 30, was carrying her two-year-old son when she stepped off the escalator at the AZG Mall in Jingzhou in Hubei province on Sunday.

She fell through the floorplates and was killed by the machinery underneath but managed to push her son to safety just in time.

Investigators found the three plates were poorly designed, allowing them to work their way loose and tilt easily. They also found the size of the plates did not match the original designs and were loosely fitted.

The manufacturer, Suzhou Shenlong Elevator Company, was accused of poor quality control, and officials have ordered all its machines operating across the province to stop service and safety checks to be carried out. The investigation also found the mall did not take proper emergency measures after its staff discovered the escalator was faulty.

Newly released video footage showed two members of staff at the shopping mall almost fell through a gap in the plates minutes before Xiang was trapped.

The footage, caught by surveillance camera, shows the two women in uniforms checking the escalator less than five minutes before the tragedy took place.

They came to the top of the moving stairway, but were startled when a metal footplate moved under their feet.

"There's a problem here. Almost fell into it," a shopping assistant was recording as saying as she pointed down.

The mall was also criticised for failing to give its staff proper training in how to deal with escalator accidents. The assistants, for instance, did not press the emergency stop button when the mother fell, investigators said.

The special investigation team was established following the accident and comprised the police and Jingzhou's quality watchdog and work safety administration.

The company in charge of escalator maintenance was also partly responsible, due to irregularities in quality control and negligence in keeping records.

AZG Mall issued a statement online on Tuesday, apologising to the woman's family and promising to "shoulder relevant responsibility".

However, family members were not satisfied. "We only saw this statement of apology on the internet. It does not seem like it was addressed to the family members, but was more like a gesture to deal with the press and public opinion," Xiang's uncle was quoted by Xinhua as saying.

Xiang's sister, who works at the mall, said employees were forced to share the apology on social media.

In 2014, 36 people died in 49 elevator and escalator accidents on the mainland, according to the Administration of Quality Supervision, Inspection and Quarantine, Xinhua reported.

Safety checks on more than two million elevators and escalators as of the end of June found almost five in every 100 elevators had problems, according to official data.